1. Field of the Invention
This invention relates to the conversion of phosphorus trihalides to phosphorus oxyhalides by oxygen oxidation. It more particularly refers to carrying out such reaction without forming an explosive mixture, and with minimum usage of oxygen.
2. Discussion of the Prior Art
The oxygen oxidation of phosphorus trihalide, particularly phosphorus trichloride, to phosphorus oxyhalide, particularly oxychloride, is well known and has been commercially practiced for some time. It is known that this oxidation proceeds quite rapidly in an exothermic manner, with suitable quality oxygen. One particular problem resides in the fact that an explosive mixture of phosphorus trihalide and gaseous oxygen forms in an oxygen containing vapor space above a liquid reaction mixture containing at least about 50% phosphorus trihalide. It is obvious that one way to avoid such explosive mixtures is to dilute the reaction mixture so that it contains less than 50% phosphorus trihalide, resolve the product into diluent and product and recycle diluent, or use a plug-flow reactor with excess oxygen. This requires the additional expense of product separation and recycle. If the diluent is a heel of product it improves the economics but it still adds capital and pumping costs.
It would, of course, be desirable to carry out this reaction in such manner as to reduce or eliminate the formation of explosive mixtures while at the same time converting. substantially all of the phosphorus trihalide within the confines of a single reactor, without excessive usage of oxygen.
One method for accomplishing this has been described in U.S. Pat. No. 3,956,463. Other pertinent references are U.S. Pat. Nos. 2,002,277; 2,741,542 and 3,052,520.